Patent GB-642683-A (GB)
Title: Dividing and square root machine
IPC: G06F7/44
Filed: 1947-10-03
Abstract: 642,683. Calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd. Oct. 3, 1947, No. 26666. Convention date, Oct. 3, 1946. [Class 106 (i)] A dividing and square root machine having a divisor register settable to represent the complement of a divisor is characterized by the provision of a read-out device adjusted by the divisor register for directly entering into a trial register an amount representing the comple-. ment of 5 times the amount whose complement is set in the divisor register. The operation of the embodiment described is set out in Fig. 2, the numerical example being 16376¸356=46. Registers 9, 12, 11, 16, 18 and 17 are represented by vertical columns subdivided according to the number of denominations provided in each register. Each stage in the computation is numbered and there are four stages to each machine cycle. The entry of the complement of the divisor in Reg. 9 and the dividend in Reg. 12 is performed, in the embodiment, by depressing keys 10, Fig. 1 f, to complete pickup circuits for magnets RG according to the quinary code. Depression of a " division " key energizes a magnet 5DR, Fig. 1e, whose function is to control the entry into the trial Reg. 11 the complement of 5 times the divisor (i.e. 82199- also a " 4 " is entered in COL. 6 of Reg. 11 for a purpose described later). The number of operations required is, in general, shortened by the trial of 5 times the divisor. The magnets RG of Reg. 9 are represented again at the bottom of Fig. 1e (the energized magnets for the present example shown cross-hatched) and control, together with the magnet 5DR, a network which is supplied with current at No. 5 stage through cam contacts C26, wire 21, contacts c of 5DR, wire 22, and the paths through the contacts shown in heavy lines to the pick-up coils of the appropriate magnets in Reg. 11 (shown cross-hatched). A trial division by complementary addition now takes place, a test circuit being established through an adding network similar to that described in Specification 629,621. If the adding of the amounts in Regs. 11 and 12 result in a tens carry into the highest order, thus indicating that 5 times the divisor will " go " into the first four digits of the dividend, a magnet would be energized which would establish circuits for the entry of the result of the cross-addition into Reg. 16 (as at stage 30). In the chosen example this is not the case and, instead, Reg. 11 is cleared. Magnet 1DR, Fig. 1e, becomes energized and magnet 5DR is de-energized, so that when cam contacts C26 close at No. 9 stage, current passes through contacts c of 1DR, wire 35, and a further network of contacts controlled by the RG magnets of Reg. 9 to set up the complement of 1 times the divisor in Reg. 11 together with a " 9 " in COL. 5 of the register. A cross-adding test results in a " go " condition and cross-addition takes place plus the " fugitive one," the result being set up in Reg. 16. Reg. 12 is cleared at No. 11 stage by the energization of a magnet RE 12, Fig. 1f. RO16 is energized to close its c contacts so that when cam contacts C26, Fig. 1f, close current passes through a network controlled by the RG magnets of Reg. 16 to set up the item (112816) standing in that register in Reg. 12. Reg. 16 is then cleared and again a cross-adding test is made resulting in a " go " condition. Thus, cycles 10 to 13, 14 to 17, 18 to 21, and 22 to 25 are similar and amount to the repeated subtraction of the divisor four times from the dividend. The quotient digit " 4 " appears in COL. 6 of Reg. 12 until a test resulting in a " no go " condition (stage 26) when circuits are established for transferring the amount in Reg. 12 to Reg. 18. Reg. 12 and Reg. 11 are cleared and then, through closed contacts C26 and RO18b, Fig. 1f, circuits are completed to a network controlled by the RG magnets of Reg. 18 to set up the digits from COLS. 1 to 5 in Reg. 12 and the quotient digit from COL. 6 in Reg. 17. At stage 29 the complement of 5 times the divisor is again entered in Reg. 12 and cross-addition now results in a " go " condition. Plug connections are made by the operator to determine the number of digits required in the answer, and when these have been obtained the machine is brought to rest with the quotient standing in Reg. 17, the remainder in Reg. 12, and the complement of the divisor still in Reg. 9. Read-out may be, for example, by closing a switch to complete the circuits of indicator lamps in a network controlled by the magnets of the registers concerned. The registers may be finally cleared by opening a main switch. Square root extraction can also be performed (the operation in this case is set out in Figs. 4a and 4b, not shown). The method employed consists in repeatedly subtracting from the amount whose root is sought the terms of the series of odd numbers 1, 3, 5, 7, 9, &c., being the differences between the series of squares 1, 4, 9, 16, 25, &c. As in the case of division, a trial is made in the first place with the sum of the first five of the terms, i.e. 1 + 3 + 5 + 7 + 9 = 25. If it goes, subtraction by complementary addition takes place and " 5 " is set up in the root register. Thereafter, the odd number 11 representing the required addition to 25 to create the next square 36 is tested against the remainder and, if it does, the root is increased to " 6 " and so on.